Functionalization of regenerated cellulose membrane via surface initiated atom transfer radical polymerization for boron removal from aqueous solution

In this study, an adsorptive membrane was prepared for efficient boron removal. Poly(glycidyl methacrylate) was grafted on the surfaces of the regenerated cellulose (RC) membrane via surface-initiated atom transfer radical polymerization, and N-methylglucamine was used to further react with epoxide rings to introduce polyhydroxyl functional groups, which served as the major binding sites for boron. The pristine and modified membranes were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), dynamic water contact angle measurement, and scanning electron microscopy. It was shown that the designed functional groups were successfully grafted onto the RC membrane, and surface modification contributed to higher boron binding capability. The optimal pH range for boron adsorption was 4-8. Under a neutral pH condition, the maximum adsorption capacity of the modified membrane was determined to be 0.75 mmol/g, which was comparable with those of commercial resins. Studies of electrolyte influence indicated the formation of inner-sphere surface complexes on the membrane surface. The ATR-FTIR and XPS analyses showed that secondary alcohol and tertiary amine groups were mainly involved in boron adsorption, and tetrahedral boron complexes were found on the membrane surface.     

Characteristics of granular boehmite and its ability to adsorb phosphate from aqueous solution

In this study, we investigated the surface properties of granulated boehmite with vinyl acetate (G-BE20) and measured the amount of phosphate it adsorbed and the effect of contact time and solution pH on the adsorption process. The specific surface area (144.9?m²/g) and the number of surface hydroxyl groups (0.88?mmol/g) of G-BE20 were smaller than those of virgin boehmite (BE), which gave a specific surface area and number of surface hydroxyl groups of 297.0?m²/g and 1.08?mmol/g, respectively. The amount of phosphate adsorbed increased with the temperature. The isotherm model of Langmuir was used to fit experimental adsorption equilibrium data for phosphate adsorption onto G-BE20. The calculated thermodynamic parameters show the spontaneous and endothermic nature of the adsorption process. The equilibrium adsorption onto G-BE20 was reached within 16?h and the amount of phosphate adsorbed was 8.4?mg/g. The kinetic mechanism of phosphate uptake was evaluated with two different models: the Largergren pseudo first- and pseudo second-order models. The data obtained showed a better fit to the pseudo second-order model (0.991) than to the pseudo first-order model (0.967), as indicated by the r values. The rate constants for the adsorption of phosphate onto G-BE20 were calculated as 0.481?1/h and 0.029?g/mg?h. The adsorption of phosphate onto G-BE20 was the maximum in the pH range 3.0-4.0.     

Synthesis of ordered mesoporous carbonaceous materials and their highly efficient capture of uranium from solutions

An extremely effortless method was applied for successful synthesis of mesoporous carbonaceous materials(MCMs) using well-ordered mesoporous silica as template. Various characterizations(scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), Raman, X-ray photoelectron spectroscopy(XPS), Brunner-Emmet-Teller(BET) and Zeta potential) confirmed that MCMs had large surface area, uniform pore size distribution, and abundant oxygen-containing functional groups. The batch techniques were employed to study U(VI) adsorption on MCMs under a wide range of experiment conditions. The adsorption kinetics of U(VI) onto MCMs were well-fitted by pseudo-second-order kinetic model, indicating a chemisorption process. The excellent adsorption capacity of MCMs calculated from the Langmuir model was 293.95 mg g~(-1) at pH 4.0. The FT-IR and XPS analyses further evidenced that the binding of U(VI) onto MCMs was ascribed to the plentiful adsorption sites(–OH and –COOH groups) in the internal mesoporous structure, which could efficiently trap guest U(VI) ions. The results presented herein revealed that MCMs were ideal adsorbents in the efficient elimination of uranium or other lanthanides/actinides from aqueous solutions, which would play an important role in environmental pollution management application.     

Blood compatibility of thermoplastic polyurethane membrane immobilized with water-soluble chitosan/dextran sulfate

Water-soluble chitosan (WSC)/dextran sulfate (DS) was immobilized onto the surface of thermoplastic polyurethane (TPU) membrane after ozone-induced graft polymerization of poly(acrylic acid) (PAA). The surface was characterized with contact angle measurement and X-ray photoelectron spectroscopy (XPS). The adsorption of human plasma fibrinogen (HPF) followed the Langmuir adsorption isotherm. The results showed that the surface density of peroxides generated and poly(acrylic acid) (PAA) grafted reached the maximum value at 20 min of ozone treatment. It was found that the WSC- and DS-immobilized amount increased with pH and the molecular weight of WSC. The membrane/water interfacial free energy increased with PAA-grafting and WSC/DS-immobilization, indicating the increasing wettability of TPU membrane. The adsorption of HPF on TPU-WSC/DS membranes could be effectively curtailed and exhibited unfavorable adsorption. Moreover, WSC/DS immobilization could effectively reduce platelet adhesion and prolong the blood coagulation time, thereby membrane improving blood compatibility of TPU membrane. In addition, the in vitro cytotoxicity test of PEC modification was non-cytotoxic according to much low growth inhibition of L929 fibroblasts. Furthermore, TPU-WSC/DS membranes exhibited higher cell viability than native TPU membrane.     

Novel hydrophobic ligand-containing hydrogel membrane matrix: preparation and application to gamma-globulins adsorption

In this study, phenylalanine as a hydrophobic ligand was covalently attached to the co-monomer methacrylochloride. Then, poly(2-hydroxyethylmethacrylate-co-methacrylamidophenyalanine) [poly(HEMA–MAPA)] membranes were prepared by UV-initiated photopolymerization of HEMA and methacrylamidophenyalanine. The γ-globulins adsorption onto these affinity membranes from aqueous solutions containing different amounts of γ-globulins at different pH was investigated in a batch system. The γ-globulins adsorption capacity of the membranes was increased as the ligand density on the membrane surface increase. The non-specific adsorption of the γ-globulins on the pHEMA membranes was negligible. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The maximum adsorption capacity (q_m) of the poly(HEMA–MAPA4) membrane for γ-globulins was 2.37 mg g⁻¹ dry membrane. The equilibrium constant (k_d) value was found to be 1.61×10⁻¹ mg ml⁻¹. More than 87% (up to 100%) of the adsorbed γ-globulins were desorbed in 120 min in the desorption medium containing 50% ethylene glycol in 1.0 M NaCl.     

DNA adsorption via Co(II) immobilized cryogels

The separation and purification of important biomolecule deoxyribonucleic acid (DNA) molecules are extremely important. The adsorption technique among these methods is highly preferred as the adsorbent cryogels are pretty much used due to large pores and the associated flow channels. In this study, the adsorption of DNA via Co(II) immobilized poly(2-hydroxyethyl methacrylate-glycidyl methacrylate) [poly(HEMA-GMA)] cryogels was performed under varying conditions of pH, interaction time, initial DNA concentration, temperature, and ionic strength. For the characterization of cryogels; swelling test, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), surface area (BET), elemental and ICP-OES analysis were performed. L-lysine amino acid was chosen as Co(II)-chelating agent and the adsorption capacity of cryogels was determined as 33.81 mg DNA/g cryogel. Adsorption of pea DNA was studied under the optimum adsorption conditions and DNA adsorption capacity of cryogels was found as 10.14 mg DNA/g cryogel. The adsorption process was examined via Langmuir and Freundlich isotherm models and the Langmuir adsorption model was determined to be more appropriate for the DNA adsorption onto cryogels.     

Removal of boron from aqueous solution by clays and modified clays

In order to increase the adsorption capacities of bentonite, sepiolite, and illite for the removal of boron form aqueous solution, the clay samples were modified by nonylammonium chloride. Specific surface areas of the samples were determined as a result of N2 adsorption-desorption at 77 K using the BET method. X-ray powder diffraction analysis of the clays and modified clays was used to determine the effects of modifying agents on the layer structure of the clays. The surface characterization of clays and modified clay samples was conducted using the FTIR technique before and after the boron adsorption. For the optimization of the adsorption of boron on clays and modified clays, the effect of pH and ionic strength was examined. The results indicate that adsorption of boron can be achieved by regulating pH values in the range of 8-10 and high ionic strength. In order to find the adsorption characteristics, Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherms were applied to the adsorption data. The data were well described by Freundlich and Dubinin-Radushkevich adsorption isotherms while the fit of Langmuir equation to adsorption data was poor. It was reached that modification of bentonite and illite with nonylammonium chloride increased the adsorption capacity for boron sorption from aqueous solution.     

Arsenic (V) adsorption on Fe3O4 nanoparticle-coated boron nitride nanotubes

Multiwalled boron nitride nanotubes (BNNTs) functionalized with Fe(3)O(4) nanoparticles (NPs) were used for arsenic removal from water solutions. Sonication followed by a heating process was developed to in situ functionalize Fe(3)O(4) NPs onto a tube surface. A batch of adsorption experiments conducted at neutral pH (6.9) and room temperature (25 °C) and using the developed nanocomposites revealed effective arsenic (V) removal. The Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherms were measured for a range of As(V) initial concentrations from 1 to 40 mg/L under the same conditions. The equilibrium data well fitted all isotherms, indicating that the mechanism for As(V) adsorption was a combination of chemical complexation and physical electrostatic attraction with a slight preference for chemisorption. The magnetite NPs functionalized on BNNTs led to a simple and rapid separation of magnetic metal-loaded adsorbents from the treated water under an external magnetic field.     

Kinetic,mechanism and equilibrium studies on removal of Pb(II) using <Emphasis Type="Italic">Citrus limettioides</Emphasis> peel and seed carbon

The sorption behaviour of Pb(II) ions onto activated carbon prepared from Citrus limettioides peel (CLPC) and seed (CLSC), which is a novel waste material, was evaluated as a function of contact time, pH, adsorbent dose, ionic strength, initial metal ion concentration and temperature in batch adsorption processes with raw Citrus limettioides peel (CLP) and seed (CLS). The maximum uptake of lead(II) ions was obtained at pH range 4.0–6.0 for CLPC, CLSC and 5.0–6.0 for raw materials (CLP, CLS). The optimal contact time was found to be 3 h. Surface morphology and functionality of the adsorbent were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis and Fourier-transform infrared (FT-IR) spectroscopy. The equilibrium data fit well with the Langmuir isotherm, confirming monolayer coverage of lead(II) ions onto CLP, CLPC, CLS and CLSC. The Langmuir monolayer adsorption capacity of CLP, CLPC, CLS and CLSC was found to be 123.60, 166.67, 15.32 and 142.86 mg/g. The calculated thermodynamic parameters showed that the sorption process was feasible, spontaneous and exothermic in nature. Kinetic studies demonstrated that adsorption of lead(II) ions followed a pseudo-second-order equation, suggesting that the adsorption process is presumably chemisorption. The adsorbents were tested for removal of Pb(II) from electroplating wastewater in connection with the reuse and selectivity of the adsorbents.     

Synthesis of Mg(II) doped ferrihydrite-humic acid coprecipitation and its Pb(II)/Cd(II) ion sorption mechanism

A magnesium doped ferrihydrite-humic acid coprecipitation (Mg-doped Fh-HA) was synthesized by coprecipitation method. The removal of heavy metals such as Pb(II) and Cd(II) was assessed. The isotherms and kinetic studies indicated that the Mg-doped Fh-HA exhibited a remarkable Pb(II) and Cd(II) sorption capacity (maximum 120.43 mg/g and 27.7 mg/g, respectively.) in aqueous solution. The sorption of Pb(II) and Cd(II) onto best fitted pseudo-second-order kinetic equation and Langmuir model. The adsorption mechanism of Mg-doped Fh-HA on Pb(II) and Cd(II) involves surface adsorption, surface complexation and surface functional groups (such as carboxyl group, hydroxyl group). In addition, ion-exchange and precipitation cannot be ignored. The Mg-doped Fh-HA is a low-cost and high-performance adsorption material and has a wide range of application prospects.     

Performance and Mechanisms of Fluoride Removal from Groundwater by Lanthanum-aluminum-loaded Hydrothermal Palygorskite Composite

Lanthanum-aluminum loaded hydrothermal palygorskite(La-Al-HP) composite was prepared and selected as adsorbent for the fluoride removal from simulated groundwater. The adsorbent was characterized by scanning electron microscopy(SEM), Brunauer-Emmet-Teller(BET) analysis, X-ray diffraction(XRD) analysis and X-ray photoelectron spectroscopy(XPS). SEM visualization shows that the dense surface structure of raw HP appeared loose and presented micro canals after modification. The BET analysis also proved the specific surface area of La-Al-HP composite(95.58 m²/g) was higher than that of the raw HP(34.31 m²/g). Subsequently, the adsorption capacity of La-Al-HP composite was demonstrated in adsorption experiments. The kinetics of fluoride ion adsorption into La-Al-HP composite followed the pseudo-second order with a correlation coefficient of 0.997. The isotherm data was well fitted with the Langmuir model. The monolayer adsorption capacity of La-Al-HP composite was 1.30 mg/g. The XRD and XPS results reveal that the La³⁺ and Al³⁺ ions were loaded on the surface of modified HP and the fluoride ion was adsorbed onto the La-Al-HP composite. A large amount of La-Al-O composite oxide existing on the surface of La-Al-HP composite might be the immanent cause for the excellent adsorption capacity of fluoride ions.     

纳米TiO2分离富集Mo(Ⅵ)和Re(Ⅶ)

本文研究了纳米TiO2吸附剂对Mo(VI)、Re(VII)的吸附行为,考察了溶液的pH值、吸附时间、温度等因素对吸附的影响。结果表明：纳米TiO2对Mo(VI)的吸附在pH 1～8条件下,吸附率超过99%,2 mL 0.05mol/L NaOH溶液可将吸附的Mo(VI)离子完全洗脱,解吸率能达到97%。在pH 1～10范围内,纳米TiO2不吸附Re(VII), 从而达到Mo(VI)、Re(VII)分离。在2℃～50℃温度范围内,Mo(VI)的吸附过程符合Langmiur等温式,纳米TiO2对Mo(VI)的最大吸附容量从11.51mg g-1增加到14.19 mg g-1;纳米TiO2分离钼后,溶液剩余的铼,用活性炭吸附,在pH1～10范围内, Re(VII)的吸附率可达99%,用浓氨水进行洗脱,洗脱率可达96%;吸附过程可用准二级反应动力学模型描述,是以化学吸附为控制步骤的吸附过程;吸附等温线与Freundlich模型有较好的拟合。     

Adsorptive scavenging of cationic dyes from aquatic phase by H3PO4 activated Indian jujube (Ziziphus mauritiana) seeds based activated carbon: Isotherm,kinetics, and thermodynamic study

In the present work, a cost-effective Indian jujube seeds derived activated carbon (IJSAC) prepared via o-phosphoric acid chemical activation, is studied for the sequestration of acriflavine (AF) and Victoria blue B (VB) from the aquatic environment. The activated carbon is characterized by Fourier transform infrared spectroscopy, N₂-adsorption/desorption isotherm, scanning electron microscopy techniques and point of zero-charge measurement. The specific surface area (S_BET) of 571 m²/g with a pore radius of 22.45 Å specifies mesoporous nature of the IJSAC. The implication of operational conditions on the adsorption of both dyes onto IJSAC assessed by batch methodology, establish the optimal conditions as dosage (1.5 and 2.5 g/L), contact time (60 min), pH (8 and 10), and initial concentration (130 and 140 mg/L) for AF and VB uptake, respectively. The Freundlich adsorption isotherm model (R² = 0.99) appropriates the equilibrium data suggesting multilayer adsorption onto heterogeneous surface sites, while pseudo-second order (R² = 0.95–0.99) is the best fit kinetic model. The liquid film and intraparticle diffusion modelling demonstrate that the adsorption process of these dyes is governed by both the steps. Maximum Langmuir adsorption capacity is 113.6 mg/g for acriflavine and 92.78 mg/g for Victoria blue B. Thermodynamic studies indicate endothermic and spontaneous adsorption of dyes. The adsorption mechanism for the uptake of AF and VB by IJSAC most probably involves hydrogen bonding, electrostatic and π-π interactions. Based on its high adsorption capacity, relatively faster kinetics, and reusability, IJSAC can be perceived as a proficient and effective adsorbent for cationic dyes removal from the liquid waste.     

Sb(III)-Imprinted Organic-Inorganic Hybrid Sorbent Prepared by Hydrothermal-Assisted Surface Imprinting Technique for Selective Adsorption of Sb(III)

Sb(III)-imprinted organic-inorganic hybrid sorbent was prepared by hydrothermal-assisted surface imprinting technique and was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy coupled to an energy dispersive spectrometer and N₂ adsorption/desorption isotherms. Hydrothermal-assisted process can improve the selectivity of the Sb(III)-imprinted hybrid sorbent for Sb(III) due to stable control of temperature and pressure. The Sb(III)-imprinted hybrid sorbent IIS indicated higher selectivity for Sb(III), had high static adsorption capacity of 37.3 mg g^–1 for Sb(III), displayed stable adsorption capacity in pH range from 4 to 8, reached an rapid adsorption equilibrium within 30 min. According to the correlation coefficient (r² > 0.99), the experimental data fitted better the pseudo-second-order kinetic model and Langmuir equilibrium isotherm.

     

The effect of humic acid on the adsorption of REEs on kaolin

For a better understanding of adsorption of the rare earth elements (REEs) onto minerals and its controlling factors, adsorption experiments were performed at pH range of from 3 to 10 with kaolin (1500 mg/L) in a matrix of various concentration of NaNO₃ and about 20 μg/L of the total REEs as well as various amounts of humic acid (HA). The adsorption of HA onto the kaolin occurred over a wide pH range and decreases with increasing pH and with increasing HA concentration. The results show that humic acid has ability to either increase or decrease the adsorption of the REEs onto kaolin, depending on pH, which may be related to their speciation distribution, interaction of HA with the mineral surface. Furthermore, the light REEs are more adsorbed onto kaolin in presence of higher concentration of HA, presumably because the increase in HA concentration in the solution enhance stronger complexing of HA with heavy REEs as compare to light REEs. The ionic strength has strong effect on the adsorption of HA and REEs onto the kaolin but little on the REEs fractionation. The results presented here indicate that mineral/water adsorption may generate the enrichment of the dissolved heavy REEs in the presence of a significant amount of humic acid, which is consistent with the fractionation of REEs in the most of natural waters.     

Adsorption of cationic copolymer nanoparticles onto bamboo fiber surfaces measured by conductometric titration

Monosized nanoparticles of 57.3 nm were prepared by cationic emulsion polymerization using a polymerizable emulsifier DMHB. The adsorption of nanoparticles onto bamboo fibers was measured by conductometric titration. The results indicated that the adsorption capacity increased with increasing contact time until 120 min. The equilibrium data for nanoparticles adsorption onto bamboo fibers were well fitted to the Langmuir equation. Moreover, the monolayer adsorption capacity of nanoparticles in the concentration range (from 0.03 g/L to 0.6 g/L) studied, as calculated from Langmuir isotherm model at 25℃, was found to be 38.61 mg/g of fibers. The SEM images showed that the nanoparticles form a uniform monolayer on bamboo fiber surfaces.     

Synthesis and Application of Co‐Poly(2‐hydroxyethyl methacrylate‐ethylene dimethacrylate) Coupled with Alizarin Yellow for Preconcentration and Determination of Lead in Water Samples by Flame Atomic Absorption Spectrometry

Poly(2‐hydroxyethyl methacrylate‐ethylene dimethacrylate) (PHEMA‐EDMA) beads were produced by free radical co‐polymerization of 2‐hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA). Then, metal complexing ligand alizarin yellow was covalently attached onto PHEMA‐EDMA beads. The resulting resin has been characterized by FT‐IR and studied for the preconcentration and determination of trace Pb(II) ion from solution samples. The optimum pH value for sorption of the metal ion was 5. The sorption capacity of functionalized resin is 100 mg.g^‐1. The chelating resin can be reused for 20 cycles of sorption‐desorption without any significant change in sorption capacity. A recovery of 96% was obtained for the metal ion with 0.1 M nitric acid as eluting agent. The equilibrium adsorption data of Pb(II) on modified resin were analyzed by Langmuir and Freundlich models. Based on equilibrium adsorption data the Langmuir and Freundlich constants were determined 2.571 and 418.7 at pH 5 and 25 °C. The method was applied for lead ions determination from well water sample.     

溶菌酶分子印迹聚合物膜的制备及其吸附性能

以溶菌酶为模板蛋白质，结合分子印迹技术在硅烷化的基质玻片上制备了溶菌酶分子印迹聚合物膜。实验优化了溶菌酶聚合物膜的印迹体系，考察了溶菌酶分子印迹聚合物膜的吸附平衡时间、最大吸附量、特异识别能力、重复使用性以及对实际样品中溶菌酶的分离情况。结果表明，在最优条件下，制备的分子印迹聚合物膜对溶菌酶具有特异吸附能力，印迹因子为3.0，吸附平衡时间为5 min，吸附行为符合Langmuir吸附模型，理论最大吸附量为42.5 mg/g，实际样品中的吸附量为30 mg/g。且此印迹聚合物膜在重复使用5次后，最大吸附量仅下降了5%，具有良好的重复使用性。该方法为复杂生物样品中目标蛋白质的分离富集提供了一种快速、高效的手段。     

Simultaneous adsorption of tetracycline,amoxicillin, and ciprofloxacin by pistachio shell powder coated with zinc oxide nanoparticles

A new adsorbent formed from pistachio shell powder that was coated with ZnO nanoparticles (CPS) was examined in terms of simultaneous adsorption of tetracycline (TEC), amoxicillin (AMO), and ciprofloxacin (CIP) from an aqueous solution. Initially, the characterization properties of a CPS-like surface morphology, functional groups, and structure were obtained using advanced analysis of TEM, SEM, XRD, EDS, and FT-IR. Post coating with ZnO nanoparticles, several surface and structural characteristics relating to the adsorption ability of the pistachio shell were significantly improved. The correlation of the kinetic data by a pseudo second-order model was successful for three antibiotics. High compatibility resulted between the TEC and CIP isotherm data and the Fruendlich model. However, the Langmuir model produced a better fit to the AMO isotherm curves. In addition, its spontaneous and exothermic nature was the main feature for the adsorption process of the three antibiotics onto CPS. Through the results, the chemical adsorption has been governed by the AMO, CIP, and TEC reaction onto the homogeneous and heterogeneous sites of CPS surfaces. The CPS exhibited a highest adsorption capacity for AMO (132.240 mg/g), then for TEC (98.717 mg/g), and CIP (92.450 mg/g). These results place CPS one among the highly efficient adsorbents that can be used to eradicate wastewater containing antibiotics.